If you pass the persuade rolls she tells you the letters just started appearing one day warning her of the immitent goblin threat and how the grove was bound to fall sooner or later, so she took the deal out of desperation to protect her own. To me it seemed like yet another branch of the Absolute wanting the druid circle out of the picture one way or the other. It's true however she just comes off as a psychotic maniac if you fail your persuades.
It's going to be a real shocker when we find out everyone we have ever met is secretly working for the Absolute. Isn't it more likely Olodan is just doing what Shadow Druids are apparently known for and is thus working independently? If not then there were two conflicting plans operating at the same time on the Absolute's part.
Maybe yes maybe no, it doesn't really matter in regard to Kagha - certainly seems like Olodan has some inside knowledge which could probably also be acquired by simply spying or different sort of collaboration (like Zhents).
In the end Kagha is just a person in over her head - consistent with desperate people in desperate circumstances theme of the Druid Grove. Ultimately it all boils down to something similar to "Wyll dilemma" whether or not the end justifies the means and I'm guessing we'll be seeing a lot of that also in regard to our Ilithid powers.
So to me she's actually very well written, once you have the full picture, but as in life you might not always get there, so that's fine too.